Activated carbon materials are widely used for a variety of applications including adsorption, liquid cleanup, gas cleanup, and gas storage. The structure and architecture of a particular activated carbon material, in particular the materials surface area, pore volume, and pore size distribution may influence the performance of the activated carbon material in these different applications. For example, the adsorption of hydrogen and methane is of interest for fuel tanks in hydrogen-powered and natural-gas-powered vehicles. It is known that the optimal pore diameter for adsorbing a molecule is about 2.7 times the critical diameter of the molecule; for example, the optimal pore diameters for hydrogen, acetylene, and methane are 6 Å, 6 Å, and 11 Å.
Existing activated carbon materials typically are produced using a combination of at least several process conditions that result in a material with the desired characteristics for a particular application. However, the causal connection between the selected process conditions and the characteristics of the resulting activated carbon material are typically not well characterized. As a consequence, there exists a bewildering array of disparate processes used to produce activated carbon materials intended for different uses.
Two existing activation methods are typically used to generate activated carbon from carbonaceous or lignocellulose precursors: 1) physical/thermal activation by a gasifying agents such as air, carbon dioxide, water vapor, oxygen; and 2) chemical activation by a one or more chemical agents such as phosphoric acid, zinc chloride, potassium hydroxide, sodium hydroxide, calcium chloride, and potassium carbonate. Physical/thermal activation methods are typically carried out at relatively high temperatures and are associated with a significantly lower yield compared to chemical activation methods. Although existing chemical activation methods may produce activated carbon materials with high surface areas, these methods do not provide for the quantitative and simultaneous control over other characteristics of the activated carbon material such as porosity and/or and pore fractions of sub-nm (<1 nm) pores and supra-nm (1-5 nm) pores, which are known to influence the performance of the activated carbon in applications such as gas adsorption.
A need exists in the art for a process of producing an activated carbon material having a prespecified surface area, pore volume, and pore size distribution. Such a process could be used to custom design an activated carbon material that is exceptionally well-suited for a selected application. Activated carbon materials produced using such a method would be useful in a wide range of applications, such as fuel tanks in vehicles, batteries, electrical capacitors, separation and purification devices, and catalysts.